A robot hand having a function for changing the manner of holding an object as well as gripping of the object is proposed (see paragraph 0039 and FIG. 5 of Japanese Patent Laid-Open No. 2005-349491). In accordance with this robot hand, when the object is gripped by a plurality of rotation finger mechanisms, the changing of the manner of holding the object is assisted by assisting a posture change of the object by an auxiliary finger mechanism.
However, when the changing of the manner of holding the object is intended by separating a certain finger mechanism among the plurality of finger mechanisms from the object without using the auxiliary finger mechanism, there is a possibility that force applied to the object from the plurality of finger mechanisms becomes unbalanced. Therefore, there is a possibility that the posture of the object with respect to the robot hand is greatly changed and the finger mechanism is slipped with respect to the object so that it results in unsuccessful changing of the manner of holding the object using the robot hand.